| ??? 10/27/04 13:04 Read: times |
#79880 - RE: Filter in ground path? No! Responding to: ???'s previous message |
Davis said:
As an example, a mains powered industrial indicator will have a 'safety earth' connection (required by law), but may have alternative earth connections via sensors, or even the physical enclosure. Eh? We are taking about YOUR 27MHz reciever modul and YOUR microcontroller board, sitting next to another. We are NOT talking about saftey grounds and we are NOT talking about sensors being connected to earth. And if you have an application with 'alternative earth connections via sensors' then you have a different problem, which cannot be solved by a ground inductor... Have a look into every modern PC and you will see that every modul is connected to chassis frame at several places, additionally signal ground of each modul is connected to each modul chassis, main board is connected to main chassis via many screws, and finally every modul gets the signal ground connected via cables. So, you have dozens over dozens of 'unnecssary' seeming connections of signal grounds and chassis grounds. AND THERE'S NOWHERE ANY INDUCTOR ISOLATING ANY GROUND!! If the safety earth is 'noisy' you have classic ground loop problems. 'Ground loops' and noise on saftey earth are different issues. And you will never be able to solve a ground loop problem by inserting a ground inductor. That's ridiculous! Take a look at the best quality (dual filter) Schaffner mains filters as an example. They also have a earth series inductor. Who tells that these filters are the best??? Have a look at your PC equipement, consisting of PC, monitor, printer, etc. Do you see any mains filter having an inductor inserted in ground? Again, inductors inserted in ground connections are only suited for very special cases, which go far beyond the scope of this forum. In your application you don't need an inductor inserted in ground connection between 27MHz reciever modul and microcontroller board, DEFINITELY NOT! Kai |
